With technology development in recent years, the following semiconductor device having nonvolatile characteristics of recorded information has been put to practical use. Specifically, a stripe pattern of a soft magnetic material is divided into two regions of different magnetization directions, and, by moving a domain wall on a boundary thereof through a spin torque phenomenon by current which is passed through the stripe, a magnetization direction at a specified location (information recording portion) of the stripe pattern is caused to be one of two different directions, which enables writing and holding information intended to be recorded as 0 or 1 with 0 and 1 being discriminated from each other. Further, by detecting the magnetization direction of the specified location by a magnetic tunnel junction element formed adjacent thereto, the state of the information intended to be recorded, i.e., whether the information is 0 or 1, can be read nondestructively.
For example, a related-art semiconductor device disclosed in Patent Document 1 and Non Patent Document 1 adopts a basic structure in which, as illustrated in FIG. 9, the semiconductor device includes, above both ends of a stripe pattern 2 of a soft magnetic material 1 that is equivalent to the information recording portion and that is a first magnetic layer, a first island pattern 4 and a second island pattern 5 of a hard magnetic material 3 as a second magnetic layer that can be magnetically coupled to the first magnetic layer, and, a magnetic tunnel junction element 6 is formed above a portion between the first island pattern 4 and the second island pattern 5 at a distance where a leakage magnetic field from a center portion of the stripe pattern 2 can be detected.
In the above-mentioned semiconductor device illustrated in FIG. 9, a structure of the information recording portion is characteristic. Specifically, the first island pattern 4 and the second island pattern 5 of the hard magnetic material 3 have different magnetization directions, and thus, two different magnetization direction regions are formed in the stripe pattern 2 of the soft magnetic material 1 which is formed in a state of being magnetically coupled thereto, and a domain wall 7 which is a boundary of the two magnetization directions is formed somewhere between the two regions. FIG. 9 illustrates a case in which the domain wall 7 is formed in proximity to the first island pattern 4.
In the semiconductor device illustrated in FIG. 9, when current is passed through the stripe pattern 2 from the first island pattern 4 side, due to the spin torque phenomenon, the domain wall 7 moves. Specifically, the magnetization direction region on the first island pattern 4 side becomes larger, and the domain wall 7 moves close to the second island pattern 5 having the different magnetization direction on the second island pattern side. At this time, if current in a reverse direction is passed, the reverse occurs, and the domain wall 7 passes the center portion of the stripe pattern 2 and returns to the proximity of the first island pattern 4 on the opposite side. In this way, the magnetization direction of the center portion of the stripe pattern 2 can be changed by the direction of passing current. This portion is the information recording portion of the semiconductor device.
Note that, the magnetic tunnel junction element 6 is disposed so as to read the magnetization direction of the center portion of the stripe pattern 2 through a leakage magnetic field, and can read whether information recorded in the information recording portion is 1 or 0. For example, when a perpendicular magnetic film is used as the stripe pattern 2, by using an in-plane magnetic film as the magnetic tunnel junction element 6, and, by disposing a center line of the stripe pattern 2 and a center of the magnetic tunnel junction element 6 at a distance from each other which is appropriate for reading the information, a semiconductor device which can read and write is formed.
Further, it is not necessary that the soft magnetic material 1 and the hard magnetic material 3 be a combination of the soft magnetic material 1 and the hard magnetic material 3 which is typically referred to, and it is sufficient that a combination of magnetic materials having different magnetic characteristics resulting in different coercive forces be adopted. It is sufficient that portions of the stripe pattern 2 of the soft magnetic material 1 in magnetic contact with the first island pattern 4 and the second island pattern 5, respectively, of the hard magnetic material 3 be magnetized so as to be magnetically in parallel.
Next, a method of manufacturing the information recording portion of the semiconductor device illustrated in FIG. 9 is described below with reference to FIG. 10A to FIG. 10E.
First, in the semiconductor device of Patent Document 1 and Non Patent Document 1, a case is described where a multilayer film in which a Co film and an Ni film are alternately stacked is used as the soft magnetic material 1, and a multilayer film in which a Co film and a Pt film are alternately stacked is used as the hard magnetic material 3.
(i) First, as illustrated in FIG. 10A, the soft magnetic material 1 in which a Co film and an Ni film are alternately stacked as the first magnetic layer, the hard magnetic material 3 in which a Co film and a Pt film are alternately stacked as the second magnetic layer, and an upper electrode material 10 which is a Ta film are formed on a substrate by a sputtering method.
(ii) Then, as illustrated in FIG. 10B, only the upper electrode material 10 and the hard magnetic material 3 are etched into shapes of the first island pattern 4 and the second island pattern 5. An appropriate mask and an argon ion milling method are used in the etching, and the etching ends when the soft magnetic material 1 is exposed.
(iii) Then, as illustrated in FIG. 10C, a mask for the stripe pattern 2 is formed on the first island pattern 4 and the second island pattern 5 which are formed, and etching is carried out by the argon ion milling method until unnecessary portions of the soft magnetic material 1 in the lowest layer are removed.
(iv) Finally, as illustrated in FIG. 10D, by etching part of the hard magnetic material 3 of the second island pattern 5, the information recording portion of the related-art semiconductor device is formed. Here, the part of the hard magnetic material 3 of the second island pattern 5 is etched so that, while using the same hard magnetic material 3, the first island pattern 4 and the second island pattern 5 have different magnetic characteristics.
(v) As the semiconductor device, after this, as illustrated in FIG. 10E, the magnetic tunnel junction element 6 is disposed so as to read the magnetization direction of the information recording portion at the center portion of the stripe pattern 2 through a leakage magnetic field to manufacture the semiconductor device which can read and write.
On the other hand, as disclosed in, for example, Patent Document 2, there are known a method of manufacturing a magnetic head, a magnetic head, and a magnetic recording device which adopt another related art that facilitates detection of an etching end point.
In Patent Document 2, as illustrated in FIG. 11, there have been proposed a method of manufacturing a magnetic head, a magnetic head, and a magnetic recording device in which, immediately below a pattern formed by etching, an end point detection layer 12 having different light emitting characteristics is locally embedded in advance in an interlayer insulating material 13 as a base, and, when etching is carried out to form a trench shape for a magnetic layer 14, exposure of the end point detection layer 12 is detected using emission spectrography. As the method of manufacturing a magnetic head, after an insulating layer 15 is formed on the interlayer insulating material 13 in which the end point detection layer 12 is embedded, a pattern is formed by etching. At that time, an etching end point is detected by a material released from the end point detection layer 12. After that, the magnetic layer 14 is embedded.